At the time, many of the Asian Christians held the celebration on Nisan 14, while most others observed Easter on the Sunday that fell within that week since the Lord was resurrected on a Sunday.At the First Council of Nicaea (325 AD), it was agreed that the date for Easter be divorced from the Hebrew calendar and the Jewish Passover.Finally in 525 AD under the direction of Pope John I, , a Scythian monk and scholar living in Rome, published new Easter tables based upon the Alexandrian computations, but converted from the Alexandrian to the Julian calendar.These computations remained in use for the Roman church and throughout Western Europe until the Gregorian calendar reform about a thousand years later.Like most scientists who helped issue in the era of modern science, Kepler gave the glory to God for all his achievements.
Obviously, as most of our astute readers would notice, we won’t find any documents dated with BC by their original author (or even with AD in the first few centuries AD).
In fact, when Julius Caesar instituted the Julian calendar (which our modern Gregorian calendar is a modified form of) in 45 BC, the year to him was still 709 meaning “from the founding of the City [of Rome]“.
Even today in Japan there are three different dating systems.
The Roman Catholic Church switched in 1583 AD and most Protestant churches adopted the Gregorian Easter either prior to, or over the next hundred years.
At this time, many European protestant churches were using astronomical Easter computations based on tables developed by Johannnes Kepler, arguably the most important astronomer of the scientific revolution and the father of “celestial mechanics” which helped explain the planetary motions.